pub static UNUSED_DOC_COMMENTS: &'static Lint
The unused_doc_comments lint detects doc comments that aren’t used by rustdoc.
unused_doc_comments
rustdoc
/// docs for x let x = 12;
{{produces}}
rustdoc does not use doc comments in all positions, and so the doc comment will be ignored. Try changing it to a normal comment with // to avoid the warning.
//